1. Field of the Invention
The present invention relates to a pump apparatus of the kind that comprises a pump including an impeller or rotor and a driving means such as an electric motor for rotating the impeller or the rotor.
2. Description of the Prior Art
In the pump apparatus of the kind specified above, the impeller or rotor is subjected to a radially inward fluid pressure which is unbalanced in the circumferential direction of the impeller or rotor for the reason to be described later in connection with the accompanying drawings. The circumferentially unbalanced radially inward fluid pressure forms a circumferentially unbalanced radially inward force which is applied through the impeller or rotor to one side of the peripheral surface of the motor shaft on which the impeller or rotor is mounted. Thus, the friction between the motor shaft and a bearing therefor is increased with a resultant increase in the friction-loss torque, in the reduction in the efficiency of the pump and, further, in the decrease of the durability of the pump. If the bearing section of the pump is worn due to the operation of the pump for a long time, the pump impeller or rotor would be offset from its initial or original parallel relationship to the mating inner surfaces of the pump housing with a resultant problem that the discharge pressure of the pump is pulsated and the pump operation produces noise.